Tennis superstar Serena Williams is pregnant and expecting to deliver her first baby this fall, her spokeswoman said on Wednesday.The confirmation, by publicist Kelly Bush Novak, came in a statement hours after the 35-year-old athlete posted a photo of herself in a yellow one-piece bathing

Tennis superstar Serena Williams is pregnant and expecting to deliver her first baby this fall, her spokeswoman said on Wednesday.

The confirmation, by publicist Kelly Bush Novak, came in a statement hours after the 35-year-old athlete posted a photo of herself in a yellow one-piece bathing suit on the social media site Snapchat with the caption "20 weeks."

Williams, who will return to the No. 1 ranking in the world next week, deleted the photo shortly after it appeared, and she waited more than six hours to make any public comment, stoking furious speculation about whether she was really expecting.

If Williams is indeed 20 weeks into her term, that would mean she was approximately two months pregnant when she captured her record 23rd Grand Slam tournament title at the Australian Open in January.

Her victory over older sister Venus Williams broke a tie with Steffi Graf for the most Grand Slam singles championships in the sport's modern era. Serena Williams has not played since, citing a knee injury.

COULD SIDELINE WIMBLEDON

Tennis star Serena Williams could take a pass on Wimbledon if physical changes from her pregnancy such as balance and blood flow affect her preparation and performance, researchers who study pregnancy in high-performing athletes said.

It would be perfectly safe for Williams to continue with rigorous training throughout pregnancy, but how quickly she would return to tournament tennis, if she so chooses, was uncertain, the researchers said.

James Pivarnik, a kinesiology professor at Michigan State University, said Williams' muscular build could forestall some of the changes that could impair performance.

Williams, who is 5 feet 9 inches (1.75 metres) and weighed 155 pounds (70 kg) according to her tennis association profile, won a 23rd Grand Slam tournament title at the Australian Open in January.

"It's not like some little 95 pound distance runner. From a size change difference, it might take longer for that to be an issue with her, depending on how she carries," said Pivarnik, who has studied the impact of pregnancy on exercise for the past three decades.

HOW PREGNANCY WILL CHANGE THINGS

In pregnancy, a woman's center of gravity shifts forward to accommodate the growing fetus, which could affect Williams' stance. Pivarnik said that Williams' size may be an advantage.

Williams has not played since January and two major events are coming up: the French Open in May and Wimbledon in July.

Pivarnik said, he would be "shocked" if Williams decided to compete at Wimbledon.

"She'd be 30 weeks. I can't see her being able to perform at a level she'd need to win," he said.

Most top athletes are able to perform very well through about the first half of pregnancy, said Dr. Bruce Young, a professor of obstetrics and gynecology at New York University Langone Medical Center.

Starting at about six months of pregnancy, a woman's balance shifts. "That would be fine if you were a swimmer. If you are a tennis player, it's a problem," Young said.

A woman's lung volume also decreases as the uterus grows and presses on the diaphragm.

"If you are competing at a very high level, that becomes a factor," Young said.

Dr. Lauren Stretcher, clinical associate professor of obstetrics and gynecology at Northwestern University Feinberg School of Medicine in Chicago, said Williams' age - 35 - increases her chances of pregnancy complications, such as developing high blood pressure.

WILL COMPETE IN 2018

Williams will not play again in 2017 but will return to the tour in 2018, her spokeswoman said.

Kelly Bush Novak told Reuters that Williams, 35, "definitely" would not be able to play again this year but "looks forward to returning in 2018.

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